Facile fabrication of sensitive surface enhanced Raman scattering substrate based on CuO/Ag core/shell nanowires

Surface enhanced-Raman spectroscopy (SEAS) is greatly affected by the substrate where excitation of the localized metal surface plasmon resonance enhances the scattering signals. This report presents the results of preparation of CuO/Ag nanowires by thermal oxidation and sputtering method. The nanowires were coated with a layer of Ag by sputtering. The samples were investigated with different characterization techniques including X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoemission spectroscopy, and Raman spectroscopy. The effect of the coating layer thickness, ranging from 20 to 240 nm, on SEAS efficiency was studied. The results show that the CuO/Ag nanowires are very sensitive SEAS substrates, which can detect the signal of Methylene Blue at low concentration of 10(-10) M. The reason for high sensitivity of the as-prepared CuO/Ag nanowires is believed to be the surface plasmon resonance in silver layer, which is further enhanced due to the charge transfer transition from Ag shell to CuO core.